At the heart of the divisive debate over abortion lies a question simultaneously medical, legal and moral: Is a fetus a person? That same query, asked in a different context, presents itself in a South Carolina dispute now before the Supreme Court.

Two women in prison for using crack cocaine while pregnant are challenging the state child-endangerment law used to convict them.The law makes it a crime to "refuse or neglect to provide the proper care and attention" so that a child "is endangered or is likely to be endangered." The South Carolina Supreme Court says a viable fetus - one able to live outside the uterus - is a child under the law.

So far, no other state's top court has allowed prosecutions of pregnant women for behavior that could affect the fetus inside them. The highest courts in Florida, Kentucky, Nevada and Ohio explicitly have disallowed such prosecutions.

But courts long have treated the "unborn viable child" as a person when someone else has killed or injured a woman's fetus. The South Carolina court calls it "absurd to recognize the viable fetus as a person for purposes of homicide laws and wrongful-death statutes but not for purposes of statutes proscribing child abuse."

Lawyers for the liberal Center for Constitutional Rights and American Civil Liberties Union, representing the two women in an appeal recently filed with the nation's highest court, say the South Carolina law, as interpreted by the state court, has two major flaws making it unconstitutional.

First, the appeal says, pregnant women cannot know with certainty when fetal viability has occurred. Second, the law fails to tell women just what conduct is prohibited.

What about women who smoke, drink or take prescription drugs during pregnancies? The appeal contends that this conduct, too, may be subject to punishment under the South Carolina law.

All such uncertainty could be avoided, the appeal says, if the justices would rule that child-abuse laws are meant to protect children, not fetuses.

The court has not yet said whether it will grant full review to the case. But a coalition of health care providers and social services workers is urging the justices to do so and strike down the state law.